fix(mr): avoid ${var/pat/$'...'} for compat42 in bash >= 4.3

In bash >= 4.3 with `shopt -s compat42` enabled, ${var/pat/$'...'}
would produce extra single quotations around the replacements.  The mr
completion uses $'\n' to insert delimiter, but the delimiter does not
need to be the newline in this context.  In this patch, we can instead
insert a space.

completions/mr

@@ -16,7 +16,7 @@ _comp_cmd_mr()
         done
     )"
     # Split [online|offline] and remove `action` placeholder.
-    commands="${commands//@(action|[\[\|\]])/$'\n'}"
+    commands="${commands//@(action|[\[\|\]])/ }"
     # Add standard aliases.
     commands="${commands} ci co ls"
     _comp_split commands "$commands"

test/runLint

@@ -67,3 +67,6 @@ gitgrep "$cmdstart"'((set|shopt)\s+[+-][a-z]+\s+posix\b|(local\s+)?POSIXLY_CORRE
 
 gitgrep '\$\{([^{}\n]|\{.*\})+/([^{}\n]|\{.*\})+/([^{}"\n]|\{.*\})*\$.*\}' \
     '$rep of ${var/pat/$rep} needs to be double-quoted for shopt -s patsub_replacement (bash >= 5.2)'
+
+gitgrep '"([^"\n]|\\.)*\$\{([^{}\n]|\{.*\})+/([^{}\n]|\{.*\})+/([^{}"\n]|\{.*\})*"([^{}"\n]|\{.*\})*\$.*\}' \
+    '$rep of "${var/pat/"$rep"}" should not be quoted for bash-4.2 or shopt -s compat42 (bash >= 4.3)'